Localized endometrial proliferations associated with pregnancy: clinical and histopathologic features of 11 cases

Eleven cases of an unusual endometrial glandular proliferation associated with early pregnancy are reported. All lesions were incidental discoveries in first-trimester gestational endometria (two elective abortions; five spontaneous abortions; three hydatidiform moles; one tubal ectopic pregnancy). Most patients (nine of 11; 82%) were older than 30 years of age; associated clinical features included oligoovulation (two), hypertension (one), and obesity (one). All lesions were small and localized, and displayed similar histological features of variable severity including glandular expansion with smooth external contours; epithelial stratification (4 to 15 layers); cribriforming (focal to extensive); mitotic activity; bland nuclear cytology; and prominent intraglandular calcifications (eight cases; 72%). Although the natural history of these distinctive pregnancy-associated endometrial lesions was unknown, nine lesions were initially classified as benign, and two were interpreted as atypical endometrial hyperplasia or focal adenocarcinoma. Follow-up for an average of 34 months (range, 18 to 56) in nine patients showed no residual endometrial lesion (seven endometrial curettages and two hysterectomies). Three patients followed by curettage have subsequently completed successful pregnancies. This unusual lesion may represent a localized, endometrial proliferation induced by pregnancy; although some endometrial lesions may display striking architectural complexity, follow-up to date suggests a benign behavior.